Strontium and neodymium isotopic compositions in sediments from Godavari, Krishna and Pennar rivers

摘要

We report here strontium (Sr) and neodymium (Nd) isotopiccompositions in bed sediments from the Godavari,Krishna and Pennar rivers, draining into the Bayof Bengal. The isotopic compositions of these sedimentsrange from 0.7190 to 0.7610 for 87Sr/86Sr and–12.04 to –23.68 for ε Nd. This wide range in Sr and Ndisotopes is derived from variable proportions of sedimentsfrom different rock types in their drainagebasins. All the three rivers have their characteristicisotopic signatures. The results display highest 87Sr/86Sr (0.7610) and most negative εNd values (–23.68) forthe sediments of Pennar river. This is attributed to thechemical weathering of gneisses and granites in itsdrainage basin. The 87Sr/86Sr and ε Nd values for theGodavari river sediments range from 0.7196 to 0.7210and –15.31 to –18.22 respectively. 87Sr/86Sr and ε Ndvalues in Krishna river sediments lie from 0.7217 to0.7301 and –12.04 to –12.78 respectively. Our resultsshow that the sedimentary load from the Godavariand Krishna rivers is primarily derived from the olderrocks in their drainage basins. It is possible that thesediments transported through peninsular Indian riverspredominantly control Sr and Nd isotope sedimentarybudget in the western Bay of Bengal.